The present invention relates to a push-pull chain which can be used in either the pushing or pulling direction without varying the length of the chain. This is accomplished by restricting the relative pivotal movement between outer links and inner links. A second invention comprises a reciprocating apparatus using this push-pull chain.
As for push-pull chains of this type, the following are known: A first one is designed in such a way that projections provided on the top surface of a link plate engage with each other to restrict the upward bending of the link plate, as disclosed in Japanese Examined Patent Publication No. 52101/1983. A second one is a push-pull chain designed as disclosed in Japanese Examined Patent Publication No. 45869/1978 so that link pins each are of a notch type having both sides cut horizontally, and the notch pin is inserted in a key-shaped pin hole bored in an outer link plate to restrict the pivotal movement of the chain. The first push-pull chain has the shortcoming that while the upward bending is restricted, the downward bending is not restricted. Although the second push-pull chain can restrict bending in both upward and downward directions, the length of the chain varies between when it is pulled and when it is pushed. This shortcoming is inconvenient, when a work connected to the chain undergoes reciprocating movement.